Automatic steam startup system



6 United States Patent [1113,536,093

[72] Inventor Lance F. Di Nonno [56] References Cited Moutflinville, New York UNITED STATES PATENTS Q 5; 123 2 2,88l,792 4/1959 Spence 137/4895 a 1 Patented Oct. 1970 33791646 8l/l968 Allsopp l37/624.l 1X [73] Assignee Spence Engineering Company Primary Examiner-Alan Cohan Walden, New York Attorney-Hopgood and Calirnafde a corporation of New York [54] AUTOMATIC STEAM STARTUP SYSTEM 5 Clams 6 Drawing ABSTRACT: In a self-operated regulating steam pressure [52] US. Cl 137/4895, regulating system, a restricting valve is connected between the 137/624. 11 main valve and the pilot valve. The restricting valve closing is [51] Int. Cl. F16k 31/36 electronically controlled in a programmed, incremental [50] Field of Search 137/4895, manner, thereby to control the steam flow through the main 624.1 1 valve.

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100% srnone: Pmur VALVE a ulu I 17,12 now mqzsmeur, CYCLE sucs '73 TOTAL mama cvcus FIGS I .nwz-wroe LA/vcs E OI-NONNO W z 4i ATTOQN EVS Patented "Oct. 27, 1970 Sheet j of 4 wwsuron I LANCE E 0i NONIVO' ATTORNDS aid m in! 5.5. 4 w y 1 l AUTOMATIC STEAM STARTUP SYSTEM My invention relates to a steam pressure regulating system; more particularly, it relates to a system for automatic startup control to safely turn steam into a cold piping system.

Prior steam systems using the Spence selfoperated regulating valves are well known, and include a main valve and a pilot valve which controls the main valve. My invention is directed to the large steam control system using such selfoperated regulating valves in which startup operation must begin from a cold steam line. The problem arises in those places which have a central source of steam, such as universities, in which steam is piped to various branches, some of which are closed during part of the day while other branch lines are operating. In the university, for exarnple, the main lines remain open, but some branch lines are closed at night. In the morning, heat must be supplied to the dormitories or to the classrooms and the heating system must be turned on since it is not economical to run the system all night.

The system, of course, must be brought on safely and noiselessly and water hammer must be eliminated. It is, therefore, well known that substantial problems exist in starting up a system which has cooled to ambient temperature. Among the problems which develop, in addition to water hammer, are transient responses and condensation of steam to water. The condensation problem may be substantial since flowing steam which, if converted into water, can be projected against apparatus in its path causing damage. The velocity of a slug of water'depends on the quantity of steam flowing, its specific volume (a function of the reduced steam pressure and temperature) and the area of the conducting pipe. For example, a slug of water propelled in a steam line at a velocity of a mile a minute or more has often broken a cast iron elbow or tee fitting.

The most common prior technique for providing startup requires a maintenance man to go to remote branch lines of the main steam system, and turn a valve on incrementally to allow the steam to flow until the system is warmed up. In the conventional system, there exists a bypass around the steam valve and a gate valve in the main line. In warming up a cold steam system, the maintenance man would slowly open up the bypass valve. The slow pace is required to hold down the rapid condensation of steam on cold pipe walls to a safe level that can be drained into steam traps and discharged from the system. The operator frequently must stand by for or minutes carefully turning more steam into the system. Once the lines are hot, rapid condensation ceases and he can raise the delivery steam pressure to its normal level. At this point the gate valve may be opened and the bypass closed so the pressure regulator can assume control. The man is now free to proceed on his rounds to other buildings to repeat the same performance.

In many systems the number of buildings and/or regulating stations is large. Many man-hours are expended daily just to turn these stations on in the morning and off at night.

One of the objects of this invention is to provide a safe, flexible and economical startup system for a steam pressure regulating system.

A further object is to provide a system for startup in a steam pressure regulating system in which the flow of steam is automatically increased in predetermined time increments.

Still another object of this invention is to provide a startup system in which the step increments are controlled by an electronic system having fixed time constants providing an incrementally increasing control voltage.

Still another object of this invention is to provide a control to the input of the pilot of a selfregulating valve in a steam pressure system to provide automatic start control.

Briefly, in this invention there is used a self operated regulating valve including a main valve, an electronically controlled restricting valve and a final control pilot valve means. There is included an electronic control system to control the restricting valve which in turn controls the flow through the pilot valve. That is, the restricting valve is modulated by the control system. The actuator is controlled by a transistorized time delay circuit which delivers a programmed, slowly increasing signal to the actuator input. The control system programs an actuator which specifically varies the restricting valve opening.

During startup the pilot valve sits wide open, completely uncontrolled, while the restricting valve, responding to the electronics system, throttles the flow of high-pressure operating steam to a bleed orifice and to the main valve. Thus, during startup, the restricting valve controls the amount of opening of the main valve. The startup period ends when the main valve opening is suflicient to build up the delivery pressure to the set point of the pilot valve. Thereafter, the pilot has control over the main valve to regulate the desired pressure.

The above-mentioned and other features and objects of this invention and the manner of attaining them will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a diagram showing the elements of the system of my invention;

FIG. 2 is a side view of the system of FIG. 1;

FIG. 3 is a circuit diagram of an embodiment of the delay modulator;

FIG. 4 is a drawing of the electromechanical transducer shown in FIGS. 1 and 2;

FIG. 5 is a diagram illustrating the time cycle for incremental pressure control; and

FIG. 6 is a detailed diagram of the electronic pressure pilot.

Referring now to FIGS. 1 and 2, there is shown a main valve 10 and a pipe or conduit 20 through which the steam passes. A pilot valve 12 is connected by conduit 14 to the main valve to control the opening and closing of said main valve. The pilot valve is actuated from pressure through conduit 13 received from downstream. The main valve has a bleed orifice 15. The action of the main valve and the pilot valve are well known and described as the Spence selfoperating, selfregulating steam pressure system.

In accordance with my invention, I have provided an intermediary restricting control valve 30 between the main valve 10 and the pilot valve 12. That is, the main valve is directly connected to the pilot valve through conduit 40 and the pilot control restricting valve 30 is inserted in this pipe sothat the pilot control valve 30 appears series-connected between the conduit sections 41 and 42.

The restricting pilot control valve 30 comprises a valve mechanism 31 which restricts the steam flow through the conduit 40. The control valve 30 is controlled by an electronic delay modulating means 32 and specifically, actuates a transducer 33 which in turn causes movement of the valve stem and modulation of the valve opening. The details of the valve components will be described later.

The pilot control valve 30, therefore, opens and-closes in accordance with electrical signals received from the delay modulator 32.

At startup, the main valve is closed and pilot valve l2'is open. It will be understood that as pilot valve 12 closes, it ordinarily causes the main valve to close. However, here, at startup, the restricting valve is closed and as it opens, the main valve opens to increase downstream pressure to an amount at which the pilot begins to close. At this point, the pilot assumes control.

The restricting valve 30 is opened in predetermined steps to control the pilot valve 12 which in turn causes the main valve 10 to open in predetermined steps.

Referring now to FIG. 5, there is shown a timing cycle diagram illustrating incremental varying of main valve opening with time during the startup period in accordance with my in vention. The first incremental opening occurs during a time T1, as illustrated in the diagram. The valve is opened beyond the desired point and then it backs ofl to reach the first plateau 0,. Once the valve settles at the opening 0,, it remains there for a period of time T2. Thereafienit is incrementally opened until it goes beyond the opening level and then it falls back to reach the interim plateau 0 It remains settled at 0 for a time period and, thereafter, the valve is incrementally opened to assume opening positions 0 0 and finally 0,, as illustrated. The entire time to open the main valve is indicated by the time T3. In order to understand the manner by which these opening levels are achieved, it will be necessary to refer to the drawings showing the delay modulator circuit, FIG. 3, as well as the transducer, FIG. 4.

FIG. 3 illustrates the circuitry means providing the valve control signals. There is shown a clock circuit 100 which produces a pulse train to drive binary fiip-flop 102, having transistors Q and Q The clock circuit shown comprises resistor R2, unijunction transistor 0,, resistor RTl and capacitor C3 in series. The clock circuit 100 has a time constant RTlCl. The output is taken between resistor R2 and base 1 of transistor Q, and delivers a negative puise train which switches the flip-flop. This results in a square wave having a pulse width of RTlCl. This pulse gates an amplifier having transistor Q which supplies charging current to a second time constant circuit comprising resistors RT2 and capacitor C6, which are series connected through diode CR 4 across transistor Q from the collector to the emitter and provide a time constant RT2C6. During the time that capacitor C6 is charging up, a stepped exponential charging curve is applied to the emitter follower, Darlington amplifier Q Q tbsough a resistor R14. A high current gain is realized through amplifier Q Q which, in the embodiment shown, supplies 03l ma. (milliamperes) DC control current to the transducer 33 of FIG. 4, which is connected at its terminals P1 and P2 across the terminals OUT and GND. That transducer may conveniently be of the type manufactured by the Barber-Colman Company of Rockford, IlL, and no further description is herein provided. The discharge time is determined by the values of capacitor C6 and resistor R14 the input impedance of amplifier Q Q and the impedance represented by resistor R13, the reverse leakage current i of transistor Q and Ri5. These impedances are sufficiently high so that the dischmge time of capacitor C6 is also very high, resulting in an essentially constant step level at the input of amplifier Q Q The clock circuit 100 produces pulses at intervals of time equal to T1 (FIG. 5). Each pulse causes the flip-flop to operate to turn the gate transistor 0, on and off. When transistor Q, is on, essentially a short circuit exists between its emitter and the collector; when transistor 0., is off, capacitor C6 charges up through resistor R10, diode CR4 and resistor RT2. However, capacitor C6 cannot discharge through diode CR-4 when transistor O is on. As a result, when transistor 0., is an effective short circuit, the voltage across capacitor C6 remains essentially constant to provide the first plateau or step level, as stated previously. When the clock circuit 160 causes the flip-flop 102 to flip, transistor O, which had been on becomes nonconductive and capacitor C6 charges up again to the next plateau.

It will be noted that the circuit of Fig. 3 comprises a safety circuit means to prevent undesired valve opening. If a short circuit were to develop through amplifier Q and Q; or, if for any reason, the voltage at the emitter of transistor 0,, were to become higher than the voltage across capacitor C6, a failure condition would exist which would cause the output signal to be higher than desired at that point in the delay cycle. This condition could cause premature full stroke of the protected main valve, defeating the purpose of the invention. To guard against this condition, a fail-safe circuit consisting of transistor Q-,, resistors R13, R15 and R16 silicon controlled rectifier, SCR-l, and relay K1 is provided. PNP transistor Q, is normally biased off because amplifier Q 0,, has a voltage gain of less than 1, therefore, the base of transistor Q, is positive with respect to its emitter. However, if the voltage on the emitter of transistor 0 for any reason, becomes higher than that across capacitor C6, transistor 0-, will be biased on and a gate pulse or level will develop across resistor R15, turning on SCR-l and removing current from across the OUT and GND terminals by the actuation of relay Kl. When reiay Kl turns on, transistor Q-, is ofi; but SCR-l remains on until system power is turned off, thereby, latching relay Kl. Reset is possible only after the faulty condition has been corrected.

Referring now to FIG. 4, once there exists current at the terminals OUT and GND, a piston is caused to move stem 220 (FIG. 6) which in turn compresses spring 208 which in turn varies diaphragm force and ultimately positions restricting valve disc, thus providing the variation in the opening in the restricted oritice valve.

The restricting valve 30, including the electronic pressure pilot, is shown in more detail in FIG. 6. Steam passes, as indicated by the arrow, through valve body 31. The valve stem 23 is moved up and down to control the amount of steam flow. Spring 208 is seated against a spring button 207, as well as the diaphragm 215. The valve spring 24%) normally urges the diaphragm in the upward position. Spring 208 works in opposition to the valve spring. The programming system operates the stem 23 which urges the spring 208 downwardly to move the diaphragm 215 downwardly. There is also shown a bracket comprising standards 209 which connect to or provide support the frame through which the piston or stem 23 passes. The standards hold the operator in proper position permitting it to exert force to compress spring 208. As illustrated, there is shown a cowl adaptor fastened by screws to the posts or standards 209. Other elements of the valve mechanism are standard and need not be described in any further detail at this time.

In summary, it will be understood that the restricting valve operates to provide automatic time delays for use with the Spence pilot valve. The unit uses an electronic delay circuit to limit the main valve travel over a predetermined delay time cycie. At the end of the delay period and the level 0, is reached, the normal pilot valve operation becomes fully operative and the startup pilot valve does not cause any additional control problems. Internal electronic control circuitry slowly increases the maximum pressure allowed to reach the main valve pilot, thus slowly increasing maximum main vaive hood pressure over the delay period. Delays of the order between 2 minutes and 2 hours may be factory set per customer specification. Since at cold system startup downstream pressure is 0 p.s.i., the control pilot will be wide open, calling for maximum valve opening to build up downstream pressure to pilot set point. Without the restricting valve, a bypass must be gradually opened manually to avoid damaging high velocity water hammer in the cold lines. The automatic control pilot eliminates the manual hand valve manipulation to safely bring on a cold steam system.

While the electronic control system can be turned on by providing a switch in the power circuit (not shown), it may be understood that other means may be provided to turn the system on, such as a thermostatic control or a time control. If a thermostatic control is used, then the steam may be applied to provide heat in offices and buiidings when the outdoor temperature falls below a certain point. Alternatively, the system may be designed with a time control to provide startup during the early morning hours or during any other time period. A clock can provide a time signal and a predetermined time in the day to actuate a switch; a thermostat can respond to outdoor temperatures to actuate a switch on or in a general area, since any common signal can be provided from a common system to turn this system on and off.

While the foregoing description sets forth the principles of the invention in connection with specific apparatus, it is to be understood that this description is made only by way of example and not as a limitation of the scope of the invention as set forth in the objects thereof and in the accompanying claims.

I claim:

1. A selfoperating pressure regulating system for startup operations comprising a main valve, regulating means for said main valve including a pilot valve, a restricting control valve operatively connected intermediate said main valve and said pilot valve to control the amount of steam applied to said pilot valve, said pilot valve further controlling said main valve in accordance with downstream pressure, and means to incrementally actuate said control valve over a predetermined programmed cycle, thereby to selectively and incrementally control the flow of steam from said main valve, said actuating means comprising solenoid means, a proportional amplifier having an output coupled to said solenoid means and an input, charging means coupled to said amplifier input, timing means and gating means coupled to said timing means and said charging means, and effective when actuated to periodically and incrementally charge said charging means to successively higher levels.

2. The system of claim 1 in which said control valve comprises an electronically controlled valve connected in series with said pilot valve.

3. The system of claim 1 in which actuating means is programmed to cause said main valve to reach successively higher degrees of opening in delayed increments of time.

4. The system of claim 3 in which at each time increment the control valve opens beyond the predetermined amount of opening, and then settles down at said predetermined amount.

5. The system of claim 2 in which said control means includes electronic timing means, said timing means including storage means, means to charge said storage means, transducer means controlling the opening of said restricting control valve, and means to periodically discharge said storage means, thereby to control said transducer means. 

